Nicely back on track and sorry to come late to the discussion. I was told a while a go that if a dog is jumping up at you and snapping, the best thing to do (need to be wearing gloves) is ram you hand into it's mouth! Basically so they can't close their mouth as your hand is in the way.
I know it's kinda similar but I've done it with our cats and they don't like it, it really pulls them up short!
As a more realistic alternative (I don't think I would do the hand/mouth thing) is take a step towards the dog and let my size 10 walking boot connect with it's mid-riff, as a great man once said... " A swift knee in the happy sacks and he'll drop like anyone"